Bacterial Cell Death Research Articles

Biofilm Demolition by [AuIII(N^N)Cl(NHC)][PF6]2 Complexes Fastened with Bipyridine and Phenanthroline Ligands; Potent Antibacterial Agents Targeting Membrane Lipid.

The development of new antibacterial drugs is essential for staying ahead of evolving antibiotic resistant bacterial (ARB) threats, ensuring effective treatment options for bacterial infections, and protecting public health. Herein, we successfully designed and synthesized two novel gold(III)- NHC complexes, [Au(1)(bpy)Cl][PF6]2 (2) and [Au(1)(phen)Cl][PF6]2 (3) based on the proligand pyridyl[1,2-a]{2-pyridylimidazol}-3-ylidene hexafluorophosphate (1•HPF6) [bpy= 2,2'-bipyridine; phen= 1,10-phenanthroline]. The synthesized complexes were characterized spectroscopically; their geometries and structural arrangements were confirmed by single crystal XRD analysis. Complexes 2 and 3 showed photoluminescence properties at room temperature and the time-resolved fluorescence decay confirmed the fluorescence lifetimes of 0.54 and 0.62 ns respectively; which were used to demonstrate their direct interaction with bacterial cells. Among the two complexes, complex 3 was found to be more potent against the bacterial strains (Staphylococcus aureus, Gram-positive and Pseudomonas aeruginosa, Gram-negative bacteria) with the MIC values of 8 µg.mL-1 and 16 µg.mL-1 respectively. Studies revealed the binding of the complexes with the fundamental phospholipids present in the cell membrane of bacteria, which was found to be the leading cause of bacterial cell death. Cytotoxicity was evaluated using an MTT assay on 293T cell lines; emphasizing the potential therapeutic uses of the Au(III)-NHC complexes to control bacterial infections.

Enhancing antibacterial efficacy through macrocyclic host complexation of fluoroquinolone antibiotics for overcoming resistance

The use of supramolecular assemblies in pharmaceuticals has garnered significant interest. Recent studies have shown that the activities of antibacterial agents can be enhanced through complexation with cyclic oligomers and metal ions. Notably, these complexes sometimes possess greater therapeutic properties than the parent drugs. To develop microbiologically potent supramolecular drugs, the complexation of macrocyclic hosts with fluoroquinolone (FQ) antibiotics was investigated. FQs are a successful family of antibiotics that target the bacterial enzymes DNA gyrase and DNA topoisomerase IV, leading to bacterial cell death through the inhibition of DNA synthesis. However, antibiotic resistance resulting from the repeated use of FQs over time has limited their effectiveness against resistant pathogens. To overcome this issue, the encapsulation of FQs in polyphenolic macrocycles was investigated. This study highlights resorcinarene, a polyphenolic host with antibacterial properties, and its ability to chemically interact with FQs. The inclusion complexation process was analyzed using NMR and FTIR techniques. The binding constants determined by 1H-NMR titration revealed that levofloxacin forms more stable complexes with resorcinarene than with β-cyclodextrin, which aligned with MD simulations. Assessment of the geometric characteristics of the inclusion complexes using 2D NMR analysis confirmed that different moieties of various FQs can fit into a single host cavity and improve activity against gram-negative bacteria. Overall, these findings suggest that encapsulation in polyphenolic macrocycles is a promising strategy for utilizing FQs against antibiotic-resistant bacteria.

Antibacterial Efficacy of Tryptophan Coordinated Silver Nanoparticles Against E. coli: Spectroscopic and Microscopic Evaluation of Bacterial Cell Death.

The capability of conventional fluorescence spectroscopy and right-angled synchronous fluorescence spectroscopy (SFS) was evaluated to quantify the antibacterial potential of chemically synthesized Tryptophan coordinated silver nanoparticles (Ag-TrpNPs). Silver nanoparticles have gained significant importance as a material of interest due to their diverse assemblies in the nanoscale range and their potent antibacterial activity. But due to toxicity of silver nanoparticles there is a dire need to coordinate these materials with some biocompatible and biodegradable molecules. The study has been focused on chemical synthesis of functional fluorescence nanomaterials based on Tryptophan molecules coordinated with silver nanoparticles (Ag-TrpNPs). The antibacterial activity of Ag-TrpNPs was assessed in bacteria due to their functional characteristics such as tuneability, biocompatibility, and bioavailability. We employed optical characterization techniques such as Ultraviolet-visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and confocal microscopy to ensure the particles formation in aqueous suspension. DLS analysis confirmed the hydrodynamic size of the nanoparticles of approximately 100nm. SEM images revealed the spherical morphology and size distribution of the Ag-TrpNPs. Escherichia coli bacterial strains were used to assess the antibacterial efficacy of the Ag-TrpNPs using fluorescence spectroscopy and imaging. Initially, the agar well plate method was employed to evaluate the antimicrobial activity of the Ag-TrpNPs. The significant zones of inhibition of size 37mm at 500µg/mL and 27mm at 15.5µg/mL were reported which indicated the efficiency of Ag-TrpNPs from higher to lower concentration. Conventional and synchronous fluorescence spectra provided evidence of bacterial cell death in aqueous suspensions to ensure the interaction of Ag-TrpNPs with E. coli bacteria at different times and concentrations. SEM was employed to investigate the interaction mechanism between Ag-TrpNPs and bacterial cells. The images revealed cell wall disintegration, leading to the leakage of cellular contents, and eventually cell death occurred.

Levofloxacin induces erythrocyte contraction leading to red cell death.

Levofloxacin, a fluoroquinolone, is an extensively used antibiotic effective against both positively and negatively staining bacteria. It works by inhibiting bacterial topoisomerase type II and topoisomerase type IV, resulting in impaired DNA synthesis and bacterial cell death. Eryptosis is another term for apoptotic cell death of erythrocyte marked by cell shrinkage, phosphatidylserine (PS) flipping, and membrane blebbing. The intent of the present research was to look at the eryptotic effect of levofloxacin by exposing erythrocytes to therapeutical doses (7, 14 µM) of levofloxacin for 48 hours. Cell size evaluation, PS subjection to outside, and calcium channel inhibition were carried out to investigate eryptosis. Oxidative stress generated by levofloxacin was measured as a putative mechanism of eryptosis using glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase activities. Similarly, hemolysis measurements demonstrated levofloxacin's cytotoxic effect. Our findings showed that therapeutic doses of levofloxacin can cause a considerable decline in antioxidant enzymes activities, as well as induce cell shrinkage, PS externalization, and hemolysis in erythrocytes. The role of calcium in triggering erythrocyte shrinkage was also confirmed. In conclusion, our findings showed that the indicated levofloxacin doses caused oxidative stress, which leads to erythrocyte death via eryptosis and hemolysis. These findings emphasize the importance of using levofloxacin with caution and the need for additional research to mitigate these side effects.

Quorum sensing orchestrates parallel cell death pathways in Vibrio cholerae via Type 6 secretion dependent and independent mechanisms.

Cell death is a fundamental biological process. In mammals, cell death sculpts tissues during development, enables injury recovery, and regulates immunity. In bacteria, cell death mechanisms remain little explored. Recently, colonies formed by the pathogen Vibrio cholerae were demonstrated to undergo a spatio-temporal program of cell death. The program is controlled by quorum sensing (QS) and driven by the Type VI secretion system. Here, we discover QS-controlled genes, called vca0646-0649 , that cause cell death in V. cholerae colonies independently of the Type VI secretion system. These findings indicate that a second cell death pathway exists in V. cholerae . The results expand our understanding of bacterial cell death mechanisms and provide insight into how cell death shapes bacterial community structure.

Outcome of Levofloxacin in the Treatment of Lower Respiratory Tract Infection

Background: Levofloxacin, a broad-spectrum fluoroquinolone antibiotic, is commonly used in treating lower respiratory tract infections (LRTIs) like pneumonia and chronic bronchitis. Its effectiveness lies in its ability to inhibit bacterial DNA gyrase, leading to bacterial cell death. Clinical outcomes of levofloxacin in LRTI treatment have generally been positive, with high rates of bacterial eradication and symptom resolution. Objective: The present research aimed to determine whether levofloxacin is an effective and safe option for treating lower respiratory tract infections. Method: From January 2022 to January 2023, researchers analyzed data from 120 patients with a lower respiratory tract infection at a tertiary hospital. Sixty patients were split evenly between a control group and an observation group. Levofloxacin was administered at the standard dosage to the control group and at a significantly higher dose to the observation group. Both the clinical efficacy and adverse reaction rates were compared and contrasted between the two groups statistically. Results: The cure rate in the observation group was 53.33 percent, which was substantially greater than the cure rate in the control group, which was 36.67 percent. There is a statistically significant difference between them (P 0.05). The overall efficacy rate of the observation group was 93.33%, significantly higher than that of the control group (73.33%). There is a statistically significant difference between them (P 0.05). There was no statistically significant difference (P>0.05) between the two groups due to the low incidence of adverse responses in both the observation and control groups. Conclusion: This research demonstrates that large dosages of levofloxacin have a stronger clinical curative impact on treating lower respiratory infections than lesser doses. It is worthwhile to promote the widespread adoption of this technique since it has the potential to greatly enhance the quality of patient care

Antimicrobial activity of apricot kernel extract loaded carboxymethyl chitosan nanoparticles against multidrug resistant wound-skin infection bacteria

In recent years, skin and soft-tissue infections, particularly due to multidrug resistance bacteria (MDR) are generating a serious health crisis to human health. Thus, the current investigation tried to find new promising alternatives such as herbal therapy and biopolymer nanotechnology to combat MDR microbes. Apricot kernels extract was prepared and its amygdalin content was determined by HPLC analysis. Carboxymethyl chitosan nanoparticles (CMC NPs) encapsulated with amygdalin extract (Am ext) were synthesized and characterized through their morphology, particle size, zeta potential and thermal analysis. The antibacterial activity of Am ext, CMC NPs and CMC-Am ext NPs were evaluated against MDR bacteria. Moreover, to confirm the antibacterial action of the samples, bacterial DNA fragmentation analysis was performed. Furthermore, the cyanide ions released from bacterial breakdown of amygdalin was confirmed using Nanocolor Cyanide 08 Test 0–31 kits. The HPLC analysis indicated that amygdalin extracted efficiently from the apricot kernels. The CMC-Am ext NPs exhibited spherical shaped and mono dispersed particles of size 28 nm; physical stability and thermal compatibility. Additionally, CMC-Am ext NPs have significant antibacterial action on all MDR microbes in synergy with Am ext. Moreover, the results confirmed that the cyanide ions were released from amygdalin breakdown by the action of bacteria. Furthermore, the DNA fragmentation analysis confirmed that both Am ext and its nano-encapsulated form caused bacterial cell death by inducing DNA damage. Therefore, these findings demonstrate CMC-Am ext NPs as a novel potential therapeutic agent which can be used as an alternative to the current antibiotics against MDR bacteria.

Lipidated DNA Nanostructures Target and Rupture Bacterial Membranes.

Chemistry has the power to endow supramolecular nanostructures with new biomedically relevant functions. Here it is reported that DNA nanostructures modified with cholesterol tags disrupt bacterial membranes to cause microbial cell death. The lipidated DNA nanostructures bind more readily to cholesterol-free bacterial membranes than to cholesterol-rich, eukaryotic membranes. These highly negatively charged, lipidated DNA nanostructures cause bacterial cell death by rupturing membranes. Strikingly, killing is mediated by clusters of barrel-shaped nanostructures that adhere to the membrane without the involvement of expected bilayer-puncturing barrels. These DNA nanomaterials may inspire the development of polymeric or small-molecule antibacterial agents that mimic the principles of selective binding and rupturing to help combat antimicrobial resistance.

Advances in Medicine: Photodynamic Therapy.

Over the past decades, medicine has made enormous progress, revolutionized by modern technologies and innovative therapeutic approaches. One of the most exciting branches of these developments is photodynamic therapy (PDT). Using a combination of light of a specific wavelength and specially designed photosensitizing substances, PDT offers new perspectives in the fight against cancer, bacterial infections, and other diseases that are resistant to traditional treatment methods. In today's world, where there is a growing problem of drug resistance, the search for alternative therapies is becoming more and more urgent. Imagine that we could destroy cancer cells or bacteria using light, without the need to use strong chemicals or antibiotics. This is what PDT promises. By activating photosensitizers using appropriately adjusted light, this therapy can induce the death of cancer or bacterial cells while minimizing damage to surrounding healthy tissues. In this work, we will explore this fascinating method, discovering its mechanisms of action, clinical applications, and development prospects. We will also analyze the latest research and patient testimonies to understand the potential of PDT for the future of medicine.

Organic extracts from sustainable hybrid poplar hairy root cultures as potential natural antimicrobial and antibiofilm agents.

In order to meet growing consumer demands in terms of naturalness, the pharmaceutical, food, and cosmetic industries are looking for active molecules of plant origin. In this context, hairy roots are considered a promising biotechnological system for the sustainable production of compounds of interest. Poplars (genus Populus, family Salicaceae) are trees of ecological interest in temperate alluvial forests and are also cultivated for their industrial timber. Poplar trees also produce specialized metabolites with a wide range of bioactive properties. The present study aimed to assess the hybrid poplar hairy root extracts for antimicrobial and antibiofilm activities against four main life-threatening strains of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Ethyl acetate extracts from two hairy root lines (HP15-3 and HP A4-12) showed significant antibacterial properties as confirmed by disc diffusion assay. Antibiofilm activities were found to be dose dependent with significant biofilm inhibition (75-95%) recorded at 1000µg.mL-1 in all the bacterial strains tested. Dose-dependent enhancement in the release of exopolysaccharides was observed in response to treatment with extracts, possibly because of stress and bacterial cell death. Fluorescence microscopy confirmed loss of cell viability of treated bacterial cells concomitant with increased production of reactive oxygen species compared to the untreated control. Overall, this study demonstrates for the first time a high potential of poplar hairy root extracts as a natural and safe platform to produce antimicrobial agents in pharmaceutical, food, industrial water management, or cosmetic industries.

Comparative study of the structural, magnetic and electrical properties of cuprous delafossites CuBO2(B = Zn, Mn and Er) prepared using the flash auto-combustion technique

The flash auto-combustion method was utilized to produce Cu-based delafossites of CuBO2 (B = Zn, Mn, and Er). x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and x-ray photoelectron spectroscopy (XPS) were employed to verify the phase formation, surface morphology, and oxidation states of the synthesized delafossite samples. The crystallite sizes were determined to be 43, 16.76, and 21.66 nm for CuZnO2, CuMnO2, and CuErO2 nanoparticles (NPs), respectively. The magnetic characteristics of CuZnO2, CuMnO2, and CuErO2 samples were studied at room temperature, revealing their paramagnetic nature through the hysteresis effect. The Seebeck coefficient (S) for CuZnO2 was found to be positive, while it was negative for CuMnO2 and CuErO2. The thermoelectric power of CuZnO2 NPs was high, indicating their potential as materials for more efficient thermoelectric devices. Additionally, CuZnO2 exhibited an antimicrobial response against four-gram (+ve) bacteria, four-gram (-ve) bacteria, and the fungus Candida albicans (CA). The data obtained demonstrated that CuZnO2 NPs altered bacterial cell morphology, ultimately leading to bacterial cell death.

The study of honokiol as a natural product-based antimicrobial agent and its potential interaction with FtsZ protein.

Multidrug resistant bacteria have been a global health threat currently and frontline clinical treatments for these infections are very limited. To develop potent antibacterial agents with new bactericidal mechanisms is thus needed urgently to address this critical antibiotic resistance challenge. Natural products are a treasure of small molecules with high bioactive and low toxicity. In the present study, we demonstrated that a natural compound, honokiol, showed potent antibacterial activity against a number of Gram-positive bacteria including MRSA and VRE. Moreover, honokiol in combination with clinically used β-lactam antibiotics exhibits strong synergistic antimicrobial effects against drug-resistant S. aureus strains. Biochemical studies further reveal that honokiol may disrupt the GTPase activity, FtsZ polymerization, cell division. These biological impacts induced by honokiol may ultimately cause bacterial cell death. The in vivo antibacterial activity of honokiol against S. aureus infection was also verified with a biological model of G. mellonella larvae. The in vivo results support that honokiol is low toxic against the larvae and effectively increases the survival rate of the larvae infected with S. aureus. These findings demonstrate the potential of honokiol for further structural advancement as a new class of antibacterial agents with high potency against multidrug-resistant bacteria.

IS1-mediated chromosomal amplification of the arn operon leads to polymyxin B resistance in Escherichia coli B strains.

Polymyxins [colistin and polymyxin B (PMB)] comprise an important class of natural product lipopeptide antibiotics used to treat multidrug-resistant Gram-negative bacterial infections. These positively charged lipopeptides interact with lipopolysaccharide (LPS) located in the outer membrane and disrupt the permeability barrier, leading to increased uptake and bacterial cell death. Many bacteria counter polymyxins by upregulating genes involved in the biosynthesis and transfer of amine-containing moieties to increase positively charged residues on LPS. Although 4-deoxy-l-aminoarabinose (Ara4N) and phosphoethanolamine (PEtN) are highly conserved LPS modifications in Escherichia coli, different lineages exhibit variable PMB susceptibilities and frequencies of resistance for reasons that are poorly understood. Herein, we describe a mechanism prevalent in E. coli B strains that depends on specific insertion sequence 1 (IS1) elements that flank genes involved in the biosynthesis and transfer of Ara4N to LPS. Spontaneous and transient chromosomal amplifications mediated by IS1 raise the frequency of PMB resistance by 10- to 100-fold in comparison to strains where a single IS1 element located 90 kb away from the end of the arn operon has been deleted. Amplification involving IS1 becomes the dominant resistance mechanism in the absence of PEtN modification. Isolates with amplified arn operons gradually lose their PMB-resistant phenotype with passaging, consistent with classical PMB heteroresistance behavior. Analysis of the whole genome transcriptome profile showed altered expression of genes residing both within and outside of the duplicated chromosomal segment, suggesting complex phenotypes including PMB resistance can result from tandem amplification events.IMPORTANCEPhenotypic variation in susceptibility and the emergence of resistant subpopulations are major challenges to the clinical use of polymyxins. While a large database of genes and alleles that can confer polymyxin resistance has been compiled, this report demonstrates that the chromosomal insertion sequence (IS) content and distribution warrant consideration as well. Amplification of large chromosomal segments containing the arn operon by IS1 increases the Ara4N content of the lipopolysaccharide layer in Escherichia coli B lineages using a mechanism that is orthogonal to transcriptional upregulation through two-component regulatory systems. Altogether, our work highlights the importance of IS elements in modulating gene expression and generating diverse subpopulations that can contribute to phenotypic polymyxin B heteroresistance.

Film-Forming Capability and Antibacterial Activity of Surface-Deacetylated Chitin Nanocrystals: Role of Degree of Deacetylation.

Developing sustainable food-active packaging materials is a major issue in food preservation applications. Chitin nanocrystals (ChNCs) are regarded as unique bioderived nanomaterials due to their inherent nitrogen moiety. By tuning the chemical functionality of this nanomaterial, it is possible to affect its properties, such as film-forming capability and antibacterial activity. In this work, surface-deacetylated chitin nanocrystals (D-ChNCs) with different degrees of deacetylation (DDs) were prepared by partial deacetylation of native chitin and subsequent acid hydrolysis, and their film-forming capability and antibacterial activity were studied systematically. The D-ChNCs showed favorable film-forming ability and antibacterial activity, which are closely related to their DD. With the increase in DD (from 5.7% to 45.4%), the formed transparent films based on ChNCs showed gradually increased elongation at break (from 0.5% to 2.5%) and water contact angle (from 25.5° to 87.0°), but decreased break strength (from 3.13 to 0.89 MPa), Young's modulus (from 0.84 to 0.24 MPa), and water vapor permeability (from 4.7 × 10-10 to 4.1 × 10-10g/m s Pa). Moreover, the antibacterial activity of the D-ChNCs against E. coli and S. aureus also increased with the increase of DD. This study also found that the depolarization and potential dissipation of the bacterial cell membrane induced by the contact between amino-rich D-ChNCs and bacteria through electrostatic attraction are the possible mechanisms causing bacterial cell death. This study provides a basis for understanding the effects of DD on the film-forming capability and antibacterial activity of ChNCs, which is conducive to the design of novel active packaging films based on ChNCs.

Luteolin exhibits antimicrobial actions against Salmonella Typhimurium and Escherichia coli: Impairment of cell adhesion, membrane integrity, and energy metabolism

There has been an increasing interest in phytochemicals with antimicrobial properties in food safety management. However, the mechanisms of action of phytochemicals remain mostly unknown, preventing their selective applications against biofilms of specific pathogenic bacteria. The objectives of the present study were to understand the antibiofilm and antibacterial properties of luteolin (LUT) and its modes of action against two detrimental foodborne pathogens, Salmonella enterica ser. Typhimurium and enterohemorrhagic Escherichia coli. The focus encompasses biofilm inhibition, interference with cell adhesion, disruption of membrane integrity, and dysfunctions of membrane-linked bacterial electron transport systems and energy metabolism. Our findings evidence that LUT prevents pathogenic biofilm formation on both biotic (eggshell) and abiotic (stainless steel and silicon rubber) surfaces by resisting irreversible cell adhesion and interfering with hydrophobic interactions between bacteria and contact surfaces. Our comprehensive biochemical and visual analyses further reveal that LUT mainly exhibits bactericidal activities by imposing oxidative stress on cells, leading to severe cellular structure damage, inhibition of metabolic and respiratory activities, and dysfunctions of energy metabolism, ultimately resulting in bacterial cell death. This study suggests that LUT has the potential to serve as a solution for developing effective, novel antimicrobials for improving food safety management.

Antibacterial Action of Zn2+ Ions Driven by the In Vivo Formed ZnO Nanoparticles.

Antibacterial formulations based on zinc oxide nanoparticles (ZnO NPs) are widely used for antibiotic replacement in veterinary medicine and animal nutrition. However, the undesired environmental impact of ZnO NPs triggers a search for alternative, environmentally safer solutions. Here, we show that Zn2+ in its ionic form is a more eco-friendly antibacterial, and its biocidal action rivals that of ZnO NPs (<100 nm size), with a minimal biocidal concentration being 41(82) μg mL-1 vs 5 μg mL-1 of ZnO NPs, as determined for 103(106) CFU mL-1 E. coli. We demonstrate that the biocidal activity of Zn2+ ions is primarily associated with their uptake by E. coli and spontaneous in vivo transformation into insoluble ZnO nanocomposites at an internal bacterial pH of 7.7. Formed in vivo nanocomposite then damages E. coli membrane and intracellular components from the inside, by forming insoluble biocomposites, whose formation can also trigger ZnO characteristic reactions damaging the cells (e.g., by generation of high-potential reactive oxygen species). Our study defines a special route in which Zn2+ metal ions induce the death of bacterial cells, which might be common to other metal ions capable of forming semiconductor oxides and insoluble hydroxides at a slightly alkaline intracellular pH of some bacteria.

Enhanced Anti-Bacterial Activity of Arachidonic Acid against the Cariogenic Bacterium Streptococcus mutans in Combination with Triclosan and Fluoride.

Dental caries is a global health problem that requires better prevention measures. One of the goals is to reduce the prevalence of the cariogenic Gram-positive bacterium Streptococcus mutans. We have recently shown that naturally occurring arachidonic acid (AA) has both anti-bacterial and anti-biofilm activities against this bacterium. An important question is how these activities are affected by other anti-bacterial compounds commonly used in mouthwashes. Here, we studied the combined treatment of AA with chlorhexidine (CHX), cetylpyridinium chloride (CPC), triclosan, and fluoride. Checkerboard microtiter assays were performed to determine the effects on bacterial growth and viability. Biofilms were quantified using the MTT metabolic assay, crystal violet (CV) staining, and live/dead staining with SYTO 9/propidium iodide (PI) visualized by spinning disk confocal microscopy (SDCM). The bacterial morphology and the topography of the biofilms were visualized by high-resolution scanning electron microscopy (HR-SEM). The effect of selected drug combinations on cell viability and membrane potential was investigated by flow cytometry using SYTO 9/PI staining and the potentiometric dye DiOC2(3), respectively. We found that CHX and CPC had an antagonistic effect on AA at certain concentrations, while an additive effect was observed with triclosan and fluoride. This prompted us to investigate the triple treatment of AA, triclosan, and fluoride, which was more effective than either compound alone or the double treatment. We observed an increase in the percentage of PI-positive bacteria, indicating increased bacterial cell death. Only AA caused significant membrane hyperpolarization, which was not significantly enhanced by either triclosan or fluoride. In conclusion, our data suggest that AA can be used together with triclosan and fluoride to improve the efficacy of oral health care.

Design of a new porphyrin-based compound and investigation of its photosensitive properties for antibacterial photodynamic therapy

Considering the increasing number of pathogens resistant to commonly used antibiotics as well as antiseptics, there is an urgent need for antimicrobial approaches that can effectively inactivate pathogens without the risk of establishing resistance. An alternative approach in this context is antibacterial photodynamic therapy (APDT). APDT is a process that involves bacterial cell death using appropriate wavelength light energy and photosensitizer and causes the production of reactive oxygen species inside or outside the microbial cell depending on the penetration of light energy. In our study, a new porphyrin compound 4,4′-methylenebis(2-((E)-((4-(10,15,20-triphenylporphyrin-5-yl)phenyl)imino)methyl)phenol) (SP) was designed and synthesized as photosensitizer and its structure was clarified by NMR (13C and 1H) and mass determination method. Photophysical and photochemical properties were examined in detail using different methods. Singlet oxygen quantum yields were obtained as 0.48 and 0.59 by direct and indirect methods, respectively. Antibacterial activity studies have been conducted within the scope of biological activity and promising results have been obtained under LED light (500–700 nm, 265 V, 1500 LM), contributing to the antibacterial photodynamic therapy literature.

Solvent-Induced Lignin Conformation Changes Affect Synthesis and Antibacterial Performance of Silver Nanoparticle.

The emergence of antibiotic-resistant bacteria necessitates the development of novel, sustainable, and biocompatible antibacterial agents. This study addresses cytotoxicity and environmental concerns associated with traditional silver nanoparticles (AgNPs) by exploring lignin, a readily available and renewable biopolymer, as a platform for AgNPs. We present a novel one-pot synthesis method for lignin-based AgNPs (AgNPs@AL) nanocomposites, achieving rapid synthesis within 5 min. This method utilizes various organic solvents, demonstrating remarkable adaptability to a wide range of lignin-dissolving systems. Characterization reveals uniform AgNP size distribution and morphology influenced by the chosen solvent. This adaptability suggests the potential for incorporating lignin-loaded antibacterial drugs alongside AgNPs, enabling combined therapy in a single nanocomposite. Antibacterial assays demonstrate exceptional efficacy against both Gram-negative and Gram-positive bacteria, with gamma-valerolactone (GVL)-assisted synthesized AgNPs exhibiting the most potent effect. Mechanistic studies suggest a combination of factors contributes to the antibacterial activity, including direct membrane damage caused by AgNPs and sustained silver ion release, ultimately leading to bacterial cell death. This work presents a straightforward, adaptable, and rapid approach for synthesizing biocompatible AgNPs@AL nanocomposites with outstanding antibacterial activity. These findings offer a promising and sustainable alternative to traditional antibiotics, contributing to the fight against antibiotic resistance while minimizing environmental impact.

Synthesis and characterization of magnetic nanoparticles decorated by carbon layers acting as defenders against bacterial infectious agents

High stability magnetic nanocomposites wrapped by carbon layers were efficiently synthesized using electrical arc powered by single arc unit. This is sufficient to ionize the nickel, and carbon electrodes immersed in distilled water through applying strong electric field between carbon rotatory cathode and nickel anode. Nickle decorated by carbon (Ni@C) nanocomposite was fully characterized by transmission electron microscope (TEM), X-ray Diffraction (XRD), Vibrating-sample magnetometer (VSM), UV/Visible Spectrophotometer (UV), Fourier-transform infrared spectroscopy (FTIR), Particle size analyzer (PZ), Zeta potential, and X-ray photoelectron spectroscopy (XPS). Ni particle was spherical with average size equals to 17 nm wrapped by carbon where its energy band gap values were 2.84 for C, and 3.36 eV for Ni. The estimated phase percentage of nickel was 64.8 % which is higher than the percentage of carbon layers that's donating the sample the observed high stability of zeta potential was found to be 26.4 mV. The saturation magnetization (Ms) and coercivity (Hc) examined were 10.624 emu/g and 80.648 G, respectively. The antibacterial effect of the synthesized nanocomposites was tested against standard ATCC (American Type Colony Collection) strains namely Pseudomonas aeruginosa 27853, Proteus mirabilis 35659, Proteus vurgalis 13315, Klebsiella pneumoniae 13883, and Staphylococcus epidermidis 12228. Proteus vurgalis 13315 was the most resistant strain which wasn't completely eradicated after 24 h incubation with the prepared nanoparticles. Further assessments through confocal microscope and reactive oxygen species (ROS) generation percentage were done to predict the possible antibacterial mechanism of the synthesized nanocomposite. Ultimately, the combined influence of nickel ions and carbon in the prepared Ni@C nanocomposite results in the suppression of bacterial respiration and the induction of oxidative stress, ultimately leading to bacterial cell death.